The protocol of Montreal for the protection of the ozone layer led to the end of the use of chlorofluorocarbons (CFCs). Less aggressive compounds for the ozone layer, such as the hydrofluorocarbons (HFCs) e.g. HFC-134a replaced chlorofluorocarbons. These latter compounds were indeed shown to provide greenhouse gases. There exists a need for the development of technologies, which present a low ODP (ozone depletion potential) and a low GWP (global warming potential). Although the hydrofluorocarbons (HFCs), which are compounds which do not affect the ozone layer, were identified as interesting candidates, they exhibit a relatively high GWP value. There still exists the need to find compounds which exhibit a low GWP value. Hydrofluoroolefins (HFO) were identified as being possible alternatives with very low ODP and GWP values.
Several processes of production HFOs compounds, in particular of propenes, were developed.
US2009/0240090 discloses the gas-phase reaction of 1,1,1,2,3-pentachloropropane (HCC 240db) into product 2-chloro-3,3,3-trifluoropropene (HCFO 1233xf). Example 3 uses a catalyst comprised of fluorinated Cr2O3. The product 1233xf thus produced is then converted into product 2-chloro-1,1,1,2-tetrafluoropropane (244bb) in a liquid phase reaction. This product 244bb is then converted into the desired 1234yf.
WO2005/108334, example 3, discloses that 240db is passed through a flow reactor for a contact time for about 5 to 50 seconds at about 250-400° C. in the presence of 5 molar excess of HF over a 50 g ⅛-inch Cr2O3 catalyst bed to give 244db (2-chloro-1,1,1,3-tetrafluoropropane). It is further indicated that the 244db is then dehydrochlorinated by passing it over a Cr2O3 catalyst (50 g) at 425-550° C. with a contact time of 25 to 30 seconds to afford product 1234ze (1,3,3,3-tetrafluoropropene).
The literature is generally about a scheme involving preparation of 1234yf via the 244 route.
There is still a need for further processes for manufacturing 1234yf.